US Vice-President Mike Pence vowed that the United States will do everything it can to support its strong allies Ireland and the UK in ensuring Brexit does not impact on stability.

Mr Pence insisted that the relationship between the US and Ireland under President Donald Trump and Taoiseach Leo Varadkar has never been stronger.

Minutes after Air Force Two touched down at Shannon Airport at 4.20pm to open Vice-President Pence's three day Irish visit, he held a short press briefing with Tanaiste Simon Coveney.

Mr Pence specifically mentioned Brexit - and the importance the US attaches to its friendship with both Ireland and the UK.

"Let me also also assure you as Foreign Minister that we will continue to work closely with our partners in Ireland and the UK to support a Brexit plan that encourages stability and also one that keeps the strong foundation forged by the Good Friday Agreement," Mr Pence said.

"We understand these are complex issues - I will be in the UK meeting with Prime Minister Boris Johnson in just a few days."

The Indiana politician also mentioned Ireland's support for the US global security operation -and specifically thanked the Government and Shannon Airport in respect of facilitating US global troop movements.

"I want to say it is a privilege and an honour to be back on the Emerald Isle," Mr Pence said.

"I spoke to President Trump on my way here - he wanted me to extend his greetings to you and I know he has forged a strong relationship with Taoiseach (Leo) Varadkar. I look forward to my meeting with the Taoiseach tomorrow.

"I am so grateful to see how we can continue to build on what is a relationship that, as President Trump said, is as strong as it has ever been under the leadership of the Taoiseach and President Donald Trump."

US Vice President Mike Pence and the Second Lady Karen Pence arrive at Shannon Airport Photo credit: Jacob King/PA Wire

Mr Pence said the US appreciated Irish support over the onset of Hurricane Dorian - and he also thanked Ireland for its support of US security and anti-terror operations.

"We are truly grateful for the strong economic relationship that exists between our two countries. That represents some $130bn every year.

"I also want to thank my appreciation for the security partnership that exists between the US and the Republic of Ireland.

"Being here, particularly at Shannon Airport, (as) it has become such an important hub for US forces deploying overseas. I am especially mindful of the close co-ordination our two countries have had in US military operations around the world and I especially want to thank the team here at Shannon and the community for the way they welcome our troops here at all hours of the day and night giving them a warm Irish welcome as they are heading into the fight or coming home. It is not a small matter."

However, Mr Coveney did not hide Irish concerns about the potential impact of Brexit on the all-island economy and the Good Friday Agreement, which brought peace to Northern Ireland.

"I want to thank the US for the role in played in bringing peace to this island but, believe me, it is very fragile," Mr Coveney stressed.

"Brexit is a decision that the UK has made to left the EU and we respect that decision.

"We are working to facilitate it as best we can.

"But there are real Irish issues here too - Brexit has a disruptive impact in the status quo that has emerged in 21 years where we now enjoy today a border that is political but largely invisible.

"We have an all-island economy that functions in a seamless way.

"One of the big challenges of the last three years of Brexit from an Irish perspective has been how we maintain the positive momentum.

"How do we maintain the seamless all-island economy?"

Mr Coveney said the Withdrawal Agreement addressed Irish concerns in the negotiations between the UK and EU.

He stressed that Ireland now needed to see workable alternatives from the UK in respect of any elements of the agreement and, specifically, the so-called Irish Back-Stop if they are to be replaced.

"That agreement protected the seamless border on the island of Ireland," he said.

"That element from an Irish perspective is hugely important. We will continue to try to work with the British Government to try to get a deal done.

"As someone who understands Ireland well, I think you will understand why it is such an emotional issue here.

"The thought of physical border infrastructure re-emerging on the island of Ireland - border inspection posts, whether they are on the border or not - is something that we simply cannot allow."

The US Vice President responded to Mr Coveney's specific Brexit concerns.

"I am grateful for your candour," Mr Pence said.

"I just want to assure you that the US will continue to work with our partners in the UK and our partners in Ireland to facilitate the parties that are involved in all the issues in a way that works best for them.

"The accomplishments of the past 21 years (are remarkable). The US is your leading market in the export side and the UK is second. We are anxious to see our economy growing and we are anxious to see Ireland continue to grow.

"We are also anxious to see the UK and Europe prosper.

"I want to also say how proud we are of the role the US played to bring peace to this island.

"This was an historic accomplishment for the Irish people and I want to assure you that we will continue to encourage Ireland and the UK as these issues are resolved to build on the peace that was accomplished with the Good Friday Agreement."